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By M. S. Klima, M. Fofana

The use of a laboratory-scale magnetic fluid-based separator for coal separations was examined. A Frantz laboratory magnetic separator was modified by fabricating new pole pieces of the appropriate geometry to provide the proper magnetic field gradients. Two separation chambers, which were constructed of Plexiglas, were designed to fit between the pole pieces. A commercially available, water-based, ferromagnetic fluid was used as the separating medium. The separating density was changed by varying the current intensity of the electromagnet coil. Both batch and continuous separations were made using 0.59 x 0.50-mm and 0.18 x 0. 15-mm coal. The results are compared to those obtained using organic liquids.

Jan 1, 1998

By C. Bemelmans, L. Chia, T. O’Keefe

Lead alloys function effectively as oxygen-evolving anodes in copper SX-EW operations, and they are highly resistant to corrosion. However, the presence of an organic (from solvent extraction circuits) in the electrolyte seems to enhance solution line attack. Laboratory tests showed that lead is soluble in D2EHPA, Acorga and LIX 984 to a limited, yet measurable, degree. Lead alloys and various lead phases formed on the anode were tested to evaluate their effect on the corrosion process in organic media. Possible causes for anode corrosion and mechanisms responsible for their initiation are discussed.

Jan 1, 1998

By I. Fafoutis

Laboratory column studies were conducted in order to assess the effectiveness of slag and red mud reactive barriers for cleaning up leachates generated at mining and waste disposal sites and loaded with copper and manganese. Solutions containing the metals of concern were prepared by dissolving the required quantities of CuSO4?5H2O and MnSO4?H2O in distilled water so that Cu concentration was 100 ppm and Mn 20 ppm. Flow rates of 25 mL.h-1 for Cu solution and 75 mL.h-1 for Mn solution were used in order to simulate aquifer water velocities of 1 ft/d and 3 ft/d respectively. Solutions were pumped upflow, in Plexiglas laboratory columns filled with each reactive medium, using peristaltic pumps. Measurements of middle and outflow column pH, redox potential, conductivity and elements concentration were performed to provide information regarding removal mechanisms for both elements and exhaustion/inactivation rates for each reactive medium. Both reactive media showed fairly good removal efficiency over the period studied. Copper was mainly removed by precipitation and formation of Cu(OH)2 while removal of manganese was due to precipitation of Mn(OH2).

Jan 1, 2006

By Heinz Distelmeier

The New Austrian Tunneling Method was, as is well known, developed from conventional rock tunnelling. In Germany about 10 years ago the NATM began to be applied to partially stable soils by incorporated excavation and support methods to allow its use with these soils. The advantages of this tunnelling technique - adaptability, ecomomy, and quality have resulted in its widespread usage. Today, about 85 % of all mined tunnels in Germany are produced with this technology. This rapid development has resulted in about 40 companies operating within a geographical area about the same size as the state of Illinois that are capable of utilizing the NATM. In most cases German contract/award procedures allow the contractor to develop alternate design and plans. As a result of this flexibility and intense competition, safety factors have been gradually reduced to the lower limit of what could be regarded as demonstrably safe, and the utilization of the NATM has expanded to include higher risk conditions, namely * excavating larger cross sections. * working with less overburden. * work undertaken under less stable soil conditions.

Jan 1, 1983

By K. J. Stanaway

Syngenetic concentrations in clastic sediments of valuable mineral particles with specific gravities exceeding that of quartz constitute placer deposits. Two fundamentally different modes of concentration characterize "trap" and "bed" placer variants. Trap placers originate during sediment erosion or reworking. Bed placers form during episodes of sediment accumulation in a variety of depositional environments and lithofacies where mineral supply and fluid dynamics are favorable. Because trap placers are thin and generally limited in area, they rarely yield economic heavy-mineral deposits. They can become economically significant if they contain more valuable "heavies," such as gold, or if they occur within or very close to much larger but characteristically lower-grade bed placers.

Jan 1, 1993

By B. W. Cavender

Innovative mining and metallurgical operating techniques and processes can be identified and developed by analyzing changes as they occurs within the mine, plant, technology or industry. Sources of change to be monitored for innovative opportunities include unexpected successes or failures, incongruities between perceived and actual events, process needs, changes in perceptions and the development of new knowledge. Innovation can be organized, practiced and managed. The perception of change as an opportunity rather than a threat is mandatory, as is the systematic measurement of innovative performance. Innovation is enhanced by specifically designed policies regarding organizational structure and staffing, daily management practices and compensation and incentives.

Jan 1, 1996

By Werner Stahl, Karsten Keller

Vibration screens are commonly used not only in classifying bulk material but also in dewatering it. The lack of a comprehensive physical theory of dewatering often leads to difficulties in the design and operation of the vibration screens. Firstly, the dewatering of bulk material will be shown, based on a physical model. Because of the oscillatory motion of the liquid in the bulk, the inertial force of the accelerated liquid and the dripping of water out of the bulk or screen must be taken into special consideration. The physical model put forward shows the effect of the various operations parameters of dewatering screens. The comparison between dewatering theory and practice will be shown by measurements using coal, limestone, etc. Dewatering measurements, which have been conducted on a vibration screen, demonstrate that different vibration frequencies and rates of acceleration lead to different residual moistures. Finally, the possibilities of improving vibration dewatering will be described.

Jan 1, 1995

By J. Stachurski, N. A. Abdel-Khalek

The objective of this investigation was to compare the results of countercurrent, column cell flotation vs. conventional (mechanical) cell flotation for the cleaning of a sulfur ore (-0.5 mm, 27.43% S) and its discrete size fractions. The tests were carried out using diesel oil as a collector and alcohol as a frother. Generally, column flotation produced concentrates of higher grade. For example, column cell flotation produced a nonwashed concentrate of 65.3% S with a recovery of 84.1%. However, conventional cell flotation produced a rougher concentrate of lower grade (57.0% S) and higher recovery (92.5%). At a superficial-wash water velocity of 0.265 cm/sec, the column product grade increased to 76.4% S, with a slightly lower recovery (80.3%). However, a concentrate with a similar recovery but a lower grade (74% S) than that of the washed product was obtained after three cleaning stages with the conventional cell. The column gave superior results for the flotation of fine and ultrafine particles.

Jan 1, 1994

By R. W. Bartlett

Aeration curing, over- a long duration in wet- red stockpiles, shows promise as an affordable pretreatment method for oxidizing gold encapsulating sulfide minerals, and possibly organic matter, in low grade refractory ores. Following aeration pretreatment, the ore is reclaimed, neutralized, and cyanide leached by conventional practices. Large tonnages of subeconomic material, including mine stripping waste, may he converted into ore by this new technology. The results presented show that a successful application of this technology will likely require crushing to about -2 cm (-3/4 in.), followed by aeration in a wet stockpile for long periods, up m three years. Natural convection may he inadequate, hut forced air ventilation, at modest pressures and power consumption, is affordable.

Jan 1, 1991

By Y. C. Kim

To generate a most profitable, ultimate pit limit is generally the first step in mine design. This paper presents a new graph theory oriented, optimum ultimate pit limit design algorithm which will maximize the total undiscounted net profit. This algorithm performs much better than the well known Lerchs-Grossmann algorithm, in terms of the reduction in computation time and computer memory requirements. This algorithm operates on many directed trees in a graph, where each vertex in a tree represents a block in the mine model. The formation of each directed tree is based more on the ore-waste support concept than the geometry constraints alone. The general procedures of the algorithm, programming considerations and two case study results are discussed in the paper.

Jan 1, 1992

By Jaime E. Sepúlveda

Semiautogenous grinding (SAG) operators have been realizing the very significant impact of fresh feed particle size distribution on the mill grinding capacity. In actual practice, this impact may be quite difficult to assess because of the natural process variability that may also involve- concurrently other critical factors such as ore hardness. Recognizing the limitations of the empirical approach, the current publication proposes the use of mathematical models and simulators to explore and assess the net effect of feed particle size only, independent of any other factors. The simulation analysis here reported provides a basis to claim that the size distribution of the particles being ground (simply characterized by a % - 2" or similar measurement) is one of the most relevant controlling variables of the overall mill performance, regardless of the SAG circuit configuration.

Jan 1, 2005

By Helen Leung, Colin R. Phillips

The performance of personal alpha dosimeters in mixed radon daughter and thoron daughter atmospheres in Ontario uranium mines is described together with monitoring developments which enable the radon daughter working level to be determined separately. The theoretical bases for continuous and integrated working level measurements based on individual and gross counts are presented in terms of the weighting factor for combining the thoron daughter working level with the radon daughter working level, and in terms of the in-growth time of the air. Implications for the determination of working level in the presence of thoron daughters are discussed.

Jan 1, 1981

By J. Alton Burks, Robert R. Stein

This paper focuses on the noise exposure levels of miners employed on longwall production faces. Along with the increased production from longwall units has come the potential for greater noise exposures. Typical noise levels are given for the various noise sources that are present on modern longwall faces. Exposure times have typically increased since the introduction of longwall technology in this country. Representative exposure times and patterns are analyzed. Possible solutions are presented for generalized cases. Engineering controls developed by the Bureau of Mines are explained and their potential effectiveness is calculated for the cases presented. The role of hearing protectors in an overall hearing conservation program is also investigated. Recent research performed by the Bureau suggests that the actual performance level of muff -type protectors may be less than the manufacturers ratings under certain circumstances. The use of muff- type protectors is discussed and analyzed with respect to their use on longwall operations.

Jan 1, 1992

By P. Mousset-Jones, F. Calizaya

This paper explains and discusses a computer program that has been developed to determine the ventilation design parameters for complex auxiliary ventilation systems such as those found in the construction of long excavations with multiple headings. The program is based on the principle of partitioning the system into segments of finite length, and formulating and solving the resulting networks recursively. The resulting network problems are solved analytically. With this program, the size of fans can be determined in order to reduce the total leakage and minimize the flow recirculation. The application of the program is illustrated by the detailed solution of an auxiliary ventilation system proposed for the Exploratory Studies Facility (ESF) at the Yucca Mountain Project, Nevada.

Jan 1, 1995

By V. Srajer

This paper deals with the problem of efficiently selecting the most appropriate loading and hauling equipment for surface mines. Problems and factors that affect productivity and operating cost are identified. During the course of collecting the information for this study, mining companies and equipment manufacturers were interviewed to define their selection practices. The majority of mining companies prepare general specifications and ask the suppliers to mate those specifications to their product line. The mining company then evaluates various proposals on the basis of the best available deal. The following 'mines from western Canada provided information for this study: Coal Mountain, Line Creek, Quintette, Westar's Harmer mine from the Province of British Columbia, and Coal Valley, Gregg River, Highvale, Luscar from the Province of Alberta.

Jan 1, 1989

By S. K. Kawatra, S. T. Bagley, T. C. Eisele

The use of the bacteria Thiobacillus ferroxidans to catalyze pyrite dissolution in coal is well known, and recent investigations have shown that T. ferrooxidans are also capable of rapidly altering the pyrite surface to facilitate its removal from coal by froth flotation and oil agglomeration. However, the effect of reactor design on the bacterial leaching rate is poorly documented, and the ability of bacteria other than T. ferrooxidans to affect pyrite flotation has been unknown. In this study, the effect of a number of different microorganisms on the flotation of unoxidized pure mineral pyrite has been investigated, and it was shown that organisms other than T. ferrooxidans are also capable of depressing pyrite flotation. In addition, comparative studies of leaching in shake-flasks and pachuca tanks have shown that the pachuca tanks allow leaching to proceed to a greater degree and at a significantly accelerated rate.

Jan 1, 1989

By Jiqing Zhang, Jon C. Yingling, Andrzej M. Wala, Richard Ray

The purpose of this paper is to present how Computational Fluid Dynamics (CFD) simulations can be used to study the flow across the main airways of a mine ventilation system. in particular, the flow through the transition zone between the upcast shaft and main fan ductwork was investigated. These studies consider potential design modifications of this transition zone to reduce the energy cost. Although CFD has many advantages, it does not completely eliminate the need for experiments, which are still needed to validate numerical solutions. For this reason, data collected during actual mine tests and CFD simulations are compared in this pa- per. This comparison allows a better understanding of the flow phenomena. Moreover, once the numerical solutions have been validated, CFD can be used with better confidence to predict the effect of changes in ductwork configurations on energy losses. CFD reduces the number and cost of tedious experiments, while enabling a broader scope of design comparisons.

Jan 1, 1997

By Lars Olaf Höglund

MiMi has been set up to be i) visionary, ii) strategic and iii) long-term. The planning as well as the executive phases involves industry, academia and authorities in close co-operation. MiMi focuses on improved, economically efficient management of mining waste, a challenge that requires combined and integrated research efforts across discipline boundaries. The MiMi programme is financed by the Swedish Foundation for Strategic Environmental Research (MISTRA) with support from the mining industry. The first programme phase covers the period 1997 - 2000, with intentions for additional phases. Planning, experience and results from the first programme period are highlighted. INTRODUCTION Most of the mining activities in Sweden takes place in the No

Jan 1, 2000

By K. Verghese, H. M. Lee, R. P. Gardner, K. Boateng

Results of work on the development of a phenomenological model for the continuous flotation process wing short-lived radioactive tracer techniques for determining model parameters is reported. A model that incorporates a flotation first-order rate constant and a residence time distribution based on the cross-flow finite-stage (CFFS) model has been derived and investigated. The short-lived radioactive tracer techniques and the nonlinear search methods necessary to extract the model parameters have been developed. The conditions under which all the model parameters can be extracted from a single radiotracer experiment are detailed and illustrated. A micro- computer-based unique data logging system has been designed, assembled, and implemented for collecting the necessary transient radiotracer data. Results are reported for a continuous laboratory flotation process for the two systems, mica ore and coal.

Jan 1, 1987

By Dave Willis

In ME'S 1994 Powder River Basin (PRB) coal transportation article, the lead author described some destinations pursued by the railroads. As with many destinations, though, they turned out to be merely stops on the way to places that have yet to be reached. Along the way, the railroads discovered that making it better is a continuous process, not just something done in several phases. This was always known but not at the awareness level that exists in 1998 railroad environments. This update of the 1994 article includes railroad companies' plans for the future of rail transportation in the PRB.

Jan 1, 1998